The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a three-dimensional (3D) bonded semiconductor structure including two semiconductor structures having metallic structures that are directly bonded together in which the mechanical strength and the electrical contact of the metal-to-metal bonding is enhanced. The present application also relates to a method of forming such a 3D bonded semiconductor structure.
Three-dimensional (3D) integration is critical in current and in future technology development. In modern 3D integration technology development, low temperature metal-to-metal, such as, for example, copper (Cu)-to copper (Cu), direct bonding is performed to both electrically and mechanically contact two wafers. Accordingly, both mechanical bonding strength and electrical contact of the metal/metal interface are critical in order to meet the reliability requirement as well as the electrical performance requirement. There is thus a need for providing a method of forming a 3D bonded semiconductor structure that can enhance the mechanical strength as well as the electrical contact of a metal-to-metal bond.